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Date:   Thu, 19 Sep 2019 07:47:54 +0300
From:   Mike Rapoport <rppt@linux.ibm.com>
To:     Yunfeng Ye <yeyunfeng@huawei.com>
Cc:     akpm@linux-foundation.org, osalvador@suse.de, mhocko@suse.co,
        dan.j.williams@intel.com, david@redhat.com,
        richardw.yang@linux.intel.com, cai@lca.pw, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: Support memblock alloc on the exact node for
 sparse_buffer_init()
References: <af88d8ab-4088-e857-575f-9be57542e130@huawei.com>
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Hi,

On Wed, Sep 18, 2019 at 12:22:29PM +0800, Yunfeng Ye wrote:
> Currently, when memblock_find_in_range_node() fail on the exact node, it
> will use %NUMA_NO_NODE to find memblock from other nodes. At present,
> the work is good, but when the large memory is insufficient and the
> small memory is enough, we want to allocate the small memory of this
> node first, and do not need to allocate large memory from other nodes.
> 
> In sparse_buffer_init(), it will prepare large chunks of memory for page
> structure. The page management structure requires a lot of memory, but
> if the node does not have enough memory, it can be converted to a small
> memory allocation without having to allocate it from other nodes.
> 
> Add %MEMBLOCK_ALLOC_EXACT_NODE flag for this situation. Normally, the
> behavior is the same with %MEMBLOCK_ALLOC_ACCESSIBLE, only that it will
> not allocate from other nodes when a single node fails to allocate.
> 
> If large contiguous block memory allocated fail in sparse_buffer_init(),
> it will allocates small block memmory section by section later.

Did you see the sparse_buffer_init() actually falling back to allocate from a
different node? If a node does not have enough memory to hold it's own
memory map, filling only it with parts of the memory map will not make such
node usable.
 
> Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
> ---
>  include/linux/memblock.h | 1 +
>  mm/memblock.c            | 3 ++-
>  mm/sparse.c              | 2 +-
>  3 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index f491690..9a81d9c 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -339,6 +339,7 @@ static inline int memblock_get_region_node(const struct memblock_region *r)
>  #define MEMBLOCK_ALLOC_ANYWHERE	(~(phys_addr_t)0)
>  #define MEMBLOCK_ALLOC_ACCESSIBLE	0
>  #define MEMBLOCK_ALLOC_KASAN		1
> +#define MEMBLOCK_ALLOC_EXACT_NODE	2
> 
>  /* We are using top down, so it is safe to use 0 here */
>  #define MEMBLOCK_LOW_LIMIT 0
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 7d4f61a..dbd52c3c 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -277,6 +277,7 @@ static phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t size,
> 
>  	/* pump up @end */
>  	if (end == MEMBLOCK_ALLOC_ACCESSIBLE ||
> +	    end == MEMBLOCK_ALLOC_EXACT_NODE ||
>  	    end == MEMBLOCK_ALLOC_KASAN)
>  		end = memblock.current_limit;
> 
> @@ -1365,7 +1366,7 @@ static phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
>  	if (found && !memblock_reserve(found, size))
>  		goto done;
> 
> -	if (nid != NUMA_NO_NODE) {
> +	if (end != MEMBLOCK_ALLOC_EXACT_NODE && nid != NUMA_NO_NODE) {
>  		found = memblock_find_in_range_node(size, align, start,
>  						    end, NUMA_NO_NODE,
>  						    flags);
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 72f010d..828db46 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -477,7 +477,7 @@ static void __init sparse_buffer_init(unsigned long size, int nid)
>  	sparsemap_buf =
>  		memblock_alloc_try_nid_raw(size, PAGE_SIZE,
>  						addr,
> -						MEMBLOCK_ALLOC_ACCESSIBLE, nid);
> +						MEMBLOCK_ALLOC_EXACT_NODE, nid);
>  	sparsemap_buf_end = sparsemap_buf + size;
>  }
> 
> -- 
> 2.7.4.huawei.3
> 
> 

-- 
Sincerely yours,
Mike.